Why world war 2 happened? Detailed story

World War 2 occurred due to a convergence of factors including unresolved issues from World War 1, economic hardships, and aggressive expansionist policies of totalitarian regimes. Adolf Hitler's Nazi Germany aimed to overturn the Treaty of Versailles, expanding its territory and ideology. Japan sought to establish dominance in Asia. These ambitions led to invasions of Poland, China, and other nations. The failure of diplomacy, the appeasement of aggressors, and geopolitical rivalries intensified tensions. The war began in 1939 with Germany's invasion of Poland, prompting global involvement. The conflict ultimately involved most of the world's nations, resulting in profound destruction and reshaping of global politics.